IL47778A - Monitoring circuit arrangements for pilot and carrier voltages - Google Patents

Description

47778/2 Monitoring circuit arrangements for pilot and carrier voltages I t SIEMENS AKTIEMGESELLSCHAFT Ci- 45451 The present invention relates to monitoring circuit arrangements for pilot and carrier voltages, especially for use in telecommunications equipment, in which arrangement there is a trigger circuit consisting of two transistors, the base of the first transistor being connected to the voltage sources which are to be monitored both via a diode which conducts when the level is too low, and via a third transistor which conducts when the voltage is too high, and in which the trigger circuit drives a switching and alarm device, whilst a fourth transistor is provided, which has its emitter-collector path arranged between one terminal of the supply source and the base of the first transistor, the base of said fourth transistor being connected across a capacitor to the switching module.

The German Patent Specification No 2,046,723 describes one known monitoring circuit arrangement for pilot and carrier monitoring in carrier frequency channels, which essentially consists of a trigger circuit comprising two transistors. The base of the first transistor in the trigger circuit, is connected to the voltage sources being monitored both via a diode which conducts when the level is too low, and via a further transistor which conducts when the voltage is too high. In this fashion the result is achieved that the trigger circuit changes state both when the level 47778/2 Is too high and when It is too lo r so that in either case an alarm is generated and switching can be effected from a service or main generator, to bring a stand-by generator into operation.

In this known arrangement, however, a false alarm may be given when the supply voltage is first switched in, or on restoratio of the supply voltage following a failure. > one object of the present invention is to provide a monitoring circuit arrangement which avoids false alarms on switching in of the supply voltage or on restoration following a failure.

There is thus provided i accordance with an embodiment of the invention a monitoring circuit arrangement for pilot and carrier voltages in telecommunication equipment comprising a trigge circuit consisting of two transistors, the base of the first transistor being connected to the voltage sources to be monitored both via a diode which conducts when the power level is too low, and via a third transistor which conduct when the voltag is too high, in which arrangement the trigger circuit controls a switching and alarm device and a fourth transistor Is situated with its emitter-collector path between one terminal of the supply source and the base of he first transistor, the base of the fourth transistor being connected via a first condenser to the switching device,, characterized in that the base of the fourth transistor is also connected to a tap of three series-connected collector resistors of a fifth transistor, the emitter-collector path of which is connected to both terminals of the supply source and that the base of the fifth transistor is connected to the junction of a voltage divider comprising two series-connected resistors 47778/2 With such a circuit arrangement the trigger circuit is blocked in accordance with the time taken to charge the capacitor, so that during this time no alarm can be produced. Generally, the time is set at some few seconds.

The invention will now be described with reference to the drawing, which is a schematic circuit diagram of one exemplary embodiment.

Transistors 195 and 198 form a bistable trigger stage of a switching device. The base of the first transistor 195 of this trigger stage is driven both via diodes 155 and 157, and via a third transistor 191. The diodes conduct if the level is too low and therefore enable the bistable trigger stage to be driven into its second stable state, whereas when the level is too high the transistor 191 goes conductive to achieve f— the same effect. Between the base of the first transistor 195 and one terminal 11 of the supply voltage source, the emitter-collector path of a fourth tr istor 192 is arranged. The base of this fourth . transistor 192 is connectad to the junction of two resistors 57 and.58, which together with a further resistor 56 form a series chain serving as a collector load for a fifth transistor 193. The base of this fifth transistor 193 is connected to the junction of two resistors 53 and 54 which are connected in series with a capacitor 130 between the terminals 9 and 11 of the supply . source.

A reference voltage is obtained via a zener diode 163. To reduce the internal resistance of this diode, trans--istors 194 and 199- are provided.

Transistors 196 and 197 and a capacitor 133 perform functions described in detail in our German Patent Specification No. 2440098.

The mode of operation of the illustrated embodiment of a circuit arrangement constructed in accordance with the invention is as follows: At the . terminal 7 a group pilot signal is monitored to check, whether its level is in excess of or below a given level, and at a terminal 6 a 60 kHz line pilot is monitored to check whether its level is too low..

At, both inputs, in the operating state, there. is a voiltage of -7.5 v. Terminal 8 is the input for a,u. carrier and bias voltage monitoring facility, at -8v, and for the dialling-ringing frequency, monitoring facility at -7.2v. The monitoring facility is provided by a circuit comprising the transistors 195 and 198 of the trigger stage, together with transistors 200, 201, 204 and 207 or 206. In the "inoperative state", i.e.. when all the voltages are present, the transistor 195 is conductive and transistor 198 is blocked, so that transistor 200 is blocked, transistors 201 and 204 are conductive, and transistors 207 and 206 are blocked.

In, his case, no alarm is generated, i.e. there is no earth potential applied to terminals 13, 15, 12 or 14.

If one of. the voltages applied to the terminals 6, 7 or 8 drops below the permissible limiting value, then a current will flow via this terminal and the transistor 195 will block. The circuit then exhibits the following behaviour. Transistors 198 and 200 become conductive, transistors 201 and 204, lock, and transistors 207 and 206 go conductive assuming that.no earth potential appears at terminals 16 (block) and 20 ( VJ ) .

The outputs 13 (A) and 12 (B) only produce an earthing pulse, and the outputs 15 (ΖΆ) and 14 (ZB) continuously produce earth potential. A luminescent diode 176 lights up. Earth potential is disconnected from the terminal 18(u).

If the group pilot output voltage (terminal 7) deviates from its setpoint value in the presence of excess level, then transistor 191 goes conductive and blocks transistor 195 via resistors 48 and 49 and a diode 158. The further behaviour of the transistors is then in accordance with what has been stated earlier. To achieve precise response on the part of the monitoring facility, transistors 194 and 199, together with a zener diode 163 and a chain of resistors 73 to 78, produce a load-independent reference voltage. via a transistor 203, a supply voltage of -12V is produced for the amplifier, A precondition here is that a terminal 20 (w) is not at earth potential so that a transistor 202 is conductive. At the same time the transistor 206 is prepared for the production of an A-alarm. Likewise, earth potential is supplied via a diode 179 to a terminal 18 ( v_) . (At the stand-by side, the generation of an alarm is inhibited).

If one of the monitored voltages has triggered an alarm, then the alarm continues even when the previously defective voltage has regained its setpoint value. The alarm must be cancelled by operation of a push-button 215 or by applying earth potential to a terminal 21. In this case, a current briefly flows to a capacitor 131 via the base-emitter diode of the fourth transistor 192 and the resistor 57. · The fourth transistor 192 is therefore overloaded and, via a resistor 51, causes the first transistor 195 to change state so that the latter now conducts, placing the aforementioned circuit in its "inoperative state". If the fault has not been rectified, then the alarm will reappear.

After the application of a supply voltage -12V to terminal 11 relative to earth potential at terminal 9, alarm production should b¾e delayed for some seconds, so that initial switch-in of the supply voltage or its restoration following a failure does not cause an unnecessary alarm to be produced. With the supply voltage disconnected, the capacitor 130 is rapidly discharged via a diode 159 and resistors connected in series therewith. With application of a voltage between the terminals 11 and 9, via the base-emitter diode of the fifth transistor 193 and the two resistors 53 and 54, the capacitor 130 is charged up. If the fifth transistor 193 is conductive, then the fourth transistor 192 is switched in via a resistor 58. The first transistor 195 again goes conductive and the aforementioned "inoperative state" is attained.

To switch from main to stand-by carrier generation, two such circuits are needed, which are connected with one another through switching lines u_, \, w_, and x , (not shown). In the following text, I signifies the main side and II the stand-by.

In the condition in which no alarm is being produced, the transistor 204 (I) is conductive and applies earth potential via a diode 174 (I), terminal 18 (u_) , via a connecting line to terminal 20 ( w) of the stand-by side, and thence via a diode 177 (II), to block a transistor 202 (II). The supply voltage is disconnected at the stand-by side' by the transistor 203 (II).

"The production of an alarm at the main side blocks the transistor 204 (I). No current flows through the diode, 174 (I) and 177 (II), i.e. the transistors 202 (II) and 203 (II) go conductive, the supply voltage being applied to the stand-by amplifier. At the same time a transistor 205 (II) goes conductive and via a terminal 17 (ν,ΙΙ) applies earth potential to the terminal 20 (w I), whilst via diode 177 (I) it Hocks the transistors 202 (I) and 203 (I). The supply voltage is thus disconnected at the main side and the transistor 207 (I) triggers the B-alarm. The transistor 206(1) is not earthed at its emitter so that no A-alarm is produced. The A-alarm is only triggered if the monitoring facility also responds at the stand-by side, i.e. if the transistor 204 (II) is blocked, when the transistor 202 (II) remains conductive and applies earth potential via a diode 164.(11) to the emitter of the transistor 206 (II), so that the B-alarm (II) is produced simultaneously.

As long as the stand-by amplifiers carry no current, alarm production at the stand-by side by application of earth potential from _v (I) to x_ (II) is prevented by virtue of the fact thst the fourth transistor 192 (II) is held conductive via resistors 62 and 63 so that the "inoperative state" is compelled. After switching to stand-by, the possibility of alarm production remains suppressed for the duration of the switching operation, by virtue of the fact that following the removal of earth potential from x , a capacitor 132 (II) is charged up via the base-emitter diode of the fourth transistor 192(11) and the resistor 62, so that the fourth transistor 192(11) remains conductive for a certain time. Once the fault has been corrected, the alarm can be cancelled, by operation of a push-button 215, and at the same time switching back to the main side is effected. 47778/2

Claims (2)

1. A monitoring circuit arrangement for pilot and carrier voltages in telecommunication equipment comprising a trigger circuit consisting of two transistors, the base of the first transistor being connected to the voltage sources to be monitored both via a diode which conducts when the power level is too low, and via a third transistor which conducts when the voltage is too high, in which arrangement the trigger circuit controls a switching and alarm device and a fourth transistor is situated with its emitter-collector path between one terminal of the supply source and the base of the first transistor, the base of the fourth transistor being connected via a first condenser to the switching device, characterized in that the base of the fourth transistor is also connected to a tap of three series-connected collector resistors of a fifth transistor, the emitter-collector path of which is connected to both teraftials of the supply source and that the base of the fifth transistor is connected to the junction of a voltage divider comprising two series-connected resistors which are also connected to both terminals of the supply source via a second condenser.

2. A monitoring circuit arrangemen substantially as described with reference to the drawing. PARTNERS ib